Water tube boiler



July 25, 1961 Q SVENSSON 2,993,481

WATER TUBE BOILER Filed July 28, 1958 Inventor:

Gus TA v SMA/550w United States Patent O 2,993,481 WATER TUBE BOILER Gustav Svensson, Partille, Sweden, assigner to Heinrich Voi-kauf, Berlin, Germany Filed July 28, 1958, Ser. No. 751,332 Claims priority, application Germany Aug. 1, 1957 Claims. (Cl. 122-406) This invention relates generally to boilers, and more particularly has reference to a boiler of the water tube ty e.

I boiler of the kind under consideration is provided with a combustion chamber, about which is disposed a tubular framework. Said framework generally includes vertically disposed corner tubes, horizontal lower distributors, horizontal upper collectors, and tubes connected be- -tween the distributors and collectors at the front, sides, and rear of the furnace. A ceiling structure of tubes is also provided, extending over the combustion chamber.

In a boiler of this type, certain of the tubes have lower portions which are located within the furnace, that is, in positions in which they are impinged upon directly by heat produced in the combustion chamber. In conventional tube structures of the general category described, a heating surface is defined by tubes located above the combustion chamber, that is, located in positions in which they, so to speak, deline a ceiling for the combustion chamber. This heating surface is formed by bending the upper portions of the radiantly heated tubes in serpentine fashion, that is, in a plurality of convolutions. In such arrangements, the entire steam-water mix-ture must of necessity ilow from the radiantly heated lower parts of the tubes through the serpentine, ceiling-defining upper portions of the tubes. In other words, the upper portions must necessarily receive all water that arises from the radiantly heated portions of the tubes.

In such an event, one is restricted to a considerable degree in selecting eicient shapes, lengths, and diameters in the design and formation of the ceiling or overhead structure produced by the serpentine tube portions. Said restriction arises by reason of the fact that the resistance to the free flow of the mixture through the upper portions of the tubes should be kept below a prescribed, predetermined value. To keep said resistance at or below said value, one can make -the necessary bends in the tubes, and can use tubes of certain diameters, only within a restricted range.

In working toward a solution of this problem, I have ascertained that a completeiy efl'icient arrangement, that represents a solution to thedesign problems that have been discussed above, results from a particular, novel arrangement of the tubes that extend from a lower distributor to an upper collector. According to the invention, said tubes have lower portions heated by radiation within the combustion chamber and upper portions that extend into communication with a collector. The tubes have in Vassociation therewith laterally projected branch tubes extending over the combustion chamber. Both ends of the last named tubes are connected to the upper portions of the radiantly heated tubes, intermediate the opposite ends of the radiantly heated tubes.

Another feature of the invention resides in the use of a throttling device inserted into the radiantly heated riser tubes at a location between the opposite ends of the branch tubes that project laterally therefrom. By the use of throttling means as described, it has been found that circulation through laterally projecting branch tubes of U or serpentine shape is increased even though there is, in actuality, a path for the mixture extending continuously in the radiantly heated risers from the distributors to the collectors.

HCC

According to another object of the invention, it is proposed to impart to the heating surface defined by the branch tubes, that is, to the laterally projecting tubes of U-shape or serpentine shape connected at their ends to the vertical risers, the function of a convection heating surface. In imparting this characteristic to the branch tubes, I arrange the same in such a manner as to cause them to be screened from the direct radiation emanating from the combustion chamber of the furnace. In one embodiment, this screen is dened by a special tubular structure underlying the branch tubes. In this Way it has been possible to employ tubes of relatively small diameter as the branch tubes that define the convection type heating surface. This is desirable in this particular art to promote eflicient heat transfer and a concentration of the heating surface.

In general, the diameter of the U-shaped or serpentine branch tubes, that extend from the risers (which are connected as straight members directly between the distributors and collectors) will be smaller than the diameter of said risers.

The invention, in carrying out a further object thereof, further includes an arrangement wherein the laterally projecting branch tubes of U or serpentine shape that deline the convection heating surface alternate, in a modiiied form, from one to the other of -two oppositely located side walls of riser tubes. In other words, one branch tube will have its ends connected to a tube of one side wall. The next adjacent branch tube will have its ends connected to a riser tube of the other side wall. Both ybranch tubes, however, will extend side-by-side over the combustion chamber.

The present invention has, as a further advantage thereof, a characteristic wherein a relatively inexpensive heating surface, in particular a convection heating surface, can be formed. No special collectors and distributors will be necessary for the laterally projecting branch tubes that serve as the convection surface. This characteristic is further enhanced by reason of the fact that the number of welded joints will be kept at a highly desirable As still another advantage of the invention, there is the characteristic wherein water circulation Will be improved. In particular, responsive to heating or" the radiation heating surface (that is, the lower portions of the vertically disposed risers extending along the sides of the cornbustion chamber), circulation will be initiated in the convection heating surface defined by the laterally projecting branch tubes. This results from the fact that buoyancy in the radiantly heated portions of the riser tubes produces a water current in the connected, convection portions or branches.

Further objects and details of the invention will be apparent from the accompanying drawing forming a part of the present application, in which drawing two embodiments are illustrated by way of example.

In the drawing:

FIG. l is a longitudinal, vertical sectional view through a boiler according to the present invention, said boiler `being illustrated somewhat diagrammatically;

FIG. 2 is a transverse, vertical sectional view through the boiler, taken at right angles to the cutting plane of FIG. l;

FIG. 3 is a horizontal sectional view through the upper portion of the boiler, that is, through the convection heating surface including the laterally projecting branch tubes;

FIG. 4 is an enlarged, detail sectional view taken longitudinally through one of the riser tubes, showing a throttling means, and

FIG. 5 is a transverse sectional view on the same scale 3 as FIG. 4, taken transversely through the tube portion shown in FIG. 4 directly above the throttling means.

Referring to the drawing in detail, in the form of the invention shown in FIGS, 1 to 3, the boiler includes a horizontally disposed steam drum 1 extending transversely of the boiler structure at the front thereof. The steam drum is disposed at the top of the boiler structure and is supported by two downcomers 2 and 3. 'I'he downcomers are vertically disposed, extending Within the front corners of the boiler as shown to particular advantage in FIG. 3. The downcomers communicate with the steam drum at the ends of the drum, and as shown in FIG. 1, a front wall distributor 4 is connected between the downcomers 2 and 3, in communication at its opposite ends with the intermediate portions of the downcomers.

Tubes S having an approximately S-shape or serpentine shape are connected at one end to the front wall distributor, and extend inwardly and upwardly therefrom so as to cool a portion of the front wall and the ceiling of the boiler.

Referring to FIG. 2, longitudinal lower distributors 6 and 7 extend horizontally from the lower, ends of the downcomers 2 and 3, respectively, in communication therewith. The distributors 6 and 7 extend horizontally to the back of the furnace along opposite sides of the combustion chamber at the bottom of the combustion chamber. The longitudinal distributors admit water to closely spaced, vertically ascending side wall tubes or riser tubes 8. These are spaced closely apart fully from the front to the rear of the combustion chamber at opposite sides of the combustion chamber, being engaged in or against the inner surfaces of the side walls of the furnace. The side wall tubes 8, communicating at their lower ends with the distributors 6 and 7, open at their upper ends into upper longitudinal collectors 9 and 10, whichY extend along the sides of the furnace at the top thereof. The upper collectors 9 and 10 at one end are connected in communication with the drum 1. The other ends of the collectors are connected in communication with return tubes 11, 12. These, as shown in FIG. 3, extend vertically downwardly within the rear corners of the furnace.

A rearwall distributor 13 extends horizontally transversely of the rear portion of the furnace, being connected at its ends in communication with the lower portions of the return tubes 11 and 12. Distributor 13 supplies heated rear wall tubes 14 with water. The rear wall tubes 14 extend in closely spaced relation across the back of the combustion chamber, and as shown in FIG. 1, have vertical lower portions merging into forwardly, horizontally projecting upper portions which extend over the combustion chamber. The upper portions of the tubes 1,4 in turn merge at their forward ends into short, vertically upwardly projecting extensions. These are connected in communication with the upper portions of the several tubes 5. The tubes will thus carry the water flowing thereinto from the tubes 14 to a transverse upper collector 15. Collector 15 at its ends is connected in communication with the respective collectors 9 andV 10, and also is in communication at its ends with the re spective return tubes 11 and 12.

Steam transfer tubes 16 and 17 arel connected at one end to the tubes 11 and y172, respectively, and extend forwardly n overlying, spaced relation to the top Wall of the -furnace into communication with the drum 1. Y

As will be apparent from FIG. 2, the side wall tubes 8 extend as straight members lfrom end to end, directly from the distributors 6 and 7 to the associated, respective collectors 9 and 10. Therefore, it is possible for water, rising within the tubes 8 by reason of radiant heating yof the lower portion of the tubes, to travel in a straight, vertical Vpath directly from the distributors 6, 7 to collectors 9, 10.

However, as Will shortly appear from the description which` follows, a throttlng means is mounted within'the several tubes 8, transversely thereof, so as to impede the 4 free ow of water the side wall tubes 8 directly from the distributors 6, 7 to the collectors 9, 10.

In accordance with the invention, Water ascending from the lower portions of the -tubes 8, by reason of radiant heating of said lower portions due to direct exposure thereof to the hot products of combustion, is caused to flow into and through the full length of a plurality of branch tubes. Said branch tubes have been designated 18, 19 in FIG. 2, and project laterally from their associated tubes 8. There is a branch tube for each tube 8 in the example shown in FIGS. l and 3. All the tubes i18 extend from one bank of side Wall tubes, and all the tubes 19 extend from. the opposite bank of tubes 8 in alternating, closely spaced relation to the several tubes 18. This will be clearly apparent from FIG. 3.

The branch tubes 18, 19 extend directly across the top of the combustion chamber, but as Will be noted in FIG. 2, the horizontally, forwardly projecting upper portions of the tubes 14 extend as a bank of screening tubes across the bottom of the tube structure defined by the tubes 18, 19. The result of this arrangement will be discussed in greater detail hereinafter.

It is 'to be further noted that the particular shape of the 'tubes 18, 19 can be varied without departure from the spirit of the invention. In the illustrated example, said tubes are in the form of horizontally extending Us. More properly, it might be said that the tubes 18, 19 are C-shaped. Instead of being in this shape, the tubes 18, 19 could be even more serpentine, that is, each tube could have a number of return bends so as to define a plurality of convolutions in each tube 18 or 19, instead of a single C-shaped or U-shaped bend or convolution, such as has been shown in FIG. 2. In either event, the desired results will be obtained and it is not desired, except as necessarily required by the scope of the appended claims, to limit myself to the particular example shown in the drawing.

As will be noted from FIG. 2, each tube 18 or 19 is connected at both of its ends to its associated tube 8, intermediate the opposite extremities of said tube 8. In other words, each tube 18 at one end opens upon a tube 8, said tube 18 extending laterally horizontally away from the tube 8 and then having, ultimately, a reentrant or return portion which is in communication with the tube 8 at a location vertically spaced from the lrst named end of the branch tube.

Intermediate the ends of each tube 18 or 19, there is a throttling plate 20 iixedly mounted in the tube 8. 'Ihe throttle 20 is so designed as to produce a restriction of the free iloW of liquid through the tube 8, at the location of the throttle. vThis has the result of causing a predetermined quantity of the water owing upwardly within each tube 8 to ow laterally outwardly through the associated tube 18 or 19, as the case may be. Said water owing into the tube 18, 19 at a location below the throttle returns to the tube 8 above the throttle and continues its upward ow to the associated collector 9 or 10.

As will be apparent from FIGS. 2 and 3, the tubes 18, 19 branch olf from the tubes 8 of the right and left side walls in closely spaced relation. As a result, a bundle of relatively closely spaced tubes 18, 19 is formed. It is to be further noted that the tubes 8 of each side wall have an appreciably larger diameter than diameter of their associated tubes 18, 19. This predetermined difference in diameters simpliiies to a considerable degree the connection of the branch tubes to the tubes 8.

The banks'of side wall or riser tubes 8 are so arranged that the tubes from said banks or groups are very close to one another (see FIG. 1). To keep the space between immediately adjacent tubes 8 as small as possible, said tubes lare reduced to a slightly smaller diameter at the location of their connection to the collectors or distributors. Thismay be noted from FIG. 2 wherein it is seen that the tubes 8 have slightly tapered upper and lower ends.

It is also of importance to note that the horizontally, forwardly projecting upper portions of the rear wall tubes 1'4 serve as a screen for the branch tubes 18, 19, protectively screening said tubes 18, 12 against the direct radiant heat emanating from the combustion chamber. In consequence, it is possible to design the boiler structure in such a way that even with a small diameter of the tubes 18, '19 (which small diameter as previously noted facilitates their connection to the tubes 8), highly favorable conditions for heat transfer by convection are created.

In the form of the invention shown in FIGS. 1 to 3, the gases resulting from combustion of fuel within the combustion chamber pass through and impinge upon the convection heating surface deiined by the serpentine or U-shaped tubes 18, 19. rIhis will be noted from the arrows in FIG. l, showing the path of said gases. The gases are then conducted rearwardly and then downwardly to an exit 22, to pass into a flue, not shown, provided at the rear or" the rear wall tubes. It will be understood that additional heating surfaces, such as those produced by an economizer or the like, not shown, may be disposed in the downcoming portion of the llue 21.

In FIGS. 4 and 5, there is shown to particular advantage one type of throttle that could be employed. The tube 8 is provided with a slot into which a plate 23 is welded. Said plate at one location on its circumference is partly cut away to provide -a gap 24, which constitutes the restricted passage or throttle. Said passage Z4, in a preferred arrangement, is located on the heated side of the tube, that is, the side nearer the combustion chamber.

It will be apparent to those skilled in the art that many alterations and modiications of the structure shown and described may be made without departure from the spirit and essence of the invention which for that reason shall not be limited but by the scope of the appended claims.

I claim:

1. In a water tube boiler having a furnace and a ue space thereabove extending lengthwise of said boiler, a first distributor, a rst collector, a rst set of radiantly heated tubes extending between said distributor and collector, said tubes of said fust set having lower vertical portions forming a wall of said furnace space and bent upper portions forming a dense ceiling between said furnace and said ue space with passages for the combustion gases from the furnace space to the ue space at the one end of the latter thereby causing the combustion gases to ow in a substantially horizontal direction through the length of said -ue space, a second distributor, a second collector, a second set of tubes vertical throughout and extending between said second distributor and said second collector, said tubes of said second set having lower portions forming Ianother wall of said furnace space and upper portions forming a wall of said flue space, and a U-shaped branch tube for each vertical tube of said second set, said branch tubes being wholly located in said flue space and connected with both ends to the associated vertical tubes respectively so that said branch tubes yare located in planes, respectively, at right angles to the ow of the combustion gases in said flue space.

2. A boiler as in claim 1, further comprising a throttle in each tube of said second set, said throttle being located intermediate the two connections of the branch tube associated with said tube of said second set and the opening of the throttled tube cross-section being eccentric with respect to the tube axis and llocated on the heated side of the tube.

3. A boiler as in claim l, further comprising at least one nonheated return tube connected with said second distributor and second collector.

4. A boiler las in claim l, further comprising a steam separator drum, and a steam conveying tube connected between said drum and said second collector.

5. A boiler as in claim 1, further comprising a third set of tubes of the type of said second set of tubes including branch tubes, said third set forming a furnace and a ue space wall opposite that formed by said second set, so that said ceiling-forming portions of said rst set of tubes is located between said second and third set of tubes and underneath the branch tubes of said second and third set.

References Cited in the tile of this patent UNITED STATES PATENTS 1,082,312 Fouque et al Dec. 23, 1913 2,877,746 Oestreich Mar. 17, 1959 FOREIGN PATENTS 907,866 France Nov. 20, 1944 762,851 Great Britain Dec. 5, 1956 

